Design of Polypropylene Electret Melt Blown Nonwovens with Superior Filtration Efficiency Stability through Thermally Stimulated Charging

Electret filters are widely used in particulate matter filtration due to their filtration efficiency that can be greatly improved by electrostatic forces without sacrificing the air resistance. However, the attenuation of the filtration efficiency remains a challenge. In this study, we report a novel strategy for producing an electret melt blown filter with superior filtration efficiency stability through a thermally stimulated charging method. The proposed approach optimizes the crystal structure and therefore results in the increased production probability of the charge traps. In addition, the re-trapping phenomenon caused by the thermal stimulation during the charging process can greatly increase the proportion of deep charge to shallow charge and improve the charge stability. A superior electret melt blown filtration material with a high filtration efficiency of 99.65%, low pressure drop of 120 Pa, and satisfactory filtration efficiency stability was produced after three cyclic charging times. The excellent filtration performance indicated that the developed material is a good air filtration candidate component for personal protection applications.